Initialization and Shutdown

To initialize libobs, you must call obs_startup(), obs_reset_video(), and then obs_reset_audio(). After that, modules typically should be loaded.

You can load individual modules manually by calling obs_open_module(). After loading, the obs_open_module() function, you must then call obs_init_module() to initialize the module.

You can load modules automatically via two functions: obs_add_module_path() and obs_load_all_modules().

After all plugin modules have been loaded, call obs_post_load_modules().

Certain modules may optionally use a configuration storage directory, which is set as a parameter to obs_startup().

When it’s time to shut down the frontend, make sure to release all references to any objects, free any data, and then call obs_shutdown(). If for some reason any libobs objects have not been released, they will be destroyed automatically and a warning will be logged.

To detect if any general memory allocations have not been freed, call the bnum_allocs() to get the number of allocations remaining. If the number remaining is above 0, there are memory leaks.

See Initialization, Shutdown, and Information for more information.

Reconfiguring Video

Any time after initialization, video settings can be reconfigured by calling obs_reset_video() as long as no outputs are active. Audio was originally intended to have this capability as well, but currently is not able to be reset once initialized; libobs must be fully shutdown in order to reconfigure audio settings.


Displays as the name implies are used for display/preview panes. To use displays, you must have a native window handle or identifier to draw on.

First you must call obs_display_create() to initialize the display, then you must assign a draw callback with obs_display_add_draw_callback(). If you need to remove a draw callback, call obs_display_remove_draw_callback() similarly.

When drawing, to draw the main preview window (if any), call obs_render_main_texture(). If you need to render a specific source on a secondary display, you can increment its “showing” state with obs_source_inc_showing() while it’s showing in the secondary display, draw it with obs_source_video_render() in the draw callback, then when it’s no longer showing in the secondary display, call obs_source_dec_showing().

If the display needs to be resized, call obs_display_resize().

If the display needs a custom background color other than black, call obs_display_set_background_color().

If the display needs to be temporarily disabled, call obs_display_set_enabled() to disable, and obs_display_enabled() to get its enabled/disabled state.

Then call obs_display_destroy() to destroy the display when it’s no longer needed.

(Important note: do not use more than one display widget within the hierarchy of the same base window; this will cause presentation stalls on macOS.)

For an example of how displays are used with Qt, see UI/qt-display.hpp and UI/qt-display.cpp.

See Displays for more information.

Saving/Loading Objects and Object Management

The frontend is generally expected to manage its own objects, however for sources, there are some helper functions to allow easier saving/loading all sources: obs_save_sources() and obs_load_sources(). With those functions, all sources that aren’t private will automatically be saved and loaded. You can also save/load individual sources manually by using obs_save_source() and obs_load_source().

(Author’s note: I should not have written those helper functions; the downside is I had to add “private” sources that aren’t saveable via the obs_source_create_private() function. Just one of the many minor design flaws that can occur during long-term development.)

For outputs, encoders, and services, there are no helper functions, so usually you’d get their settings individually and save them as json. (See obs_output_get_settings()). You don’t have to save each object to different files individually; you’d save multiple objects together in a bigger obs_data_t object, then save that via obs_data_save_json_safe(), then load everything again via obs_data_create_from_json_file_safe().


The core, as well as scenes and sources, have a set of standard signals that are used to determine when something happens or changes.

Typically the most important signals are the Output Signals: the start, stop, starting, stopping, reconnect, reconnect_success signals in particular.

Most other signals for scenes/sources are optional if you are the only thing controlling their state. However, it’s generally recommended to watch most signals when possible for consistency. See Source Signals and Scene Signals for more information.

For example, let’s say you wanted to connect a callback to the stop signal of an output. The stop signal has two parameters: output and code. A callback for this signal would typically look something like this:

static void output_stopped(void *my_data, calldata_t *cd)
        obs_output_t *output = calldata_ptr(cd, "output");
        int code = calldata_int(cd, "code");


(Note that callbacks are not thread-safe.)

Then to connect it to the stop signal, you use the signal_handler_connect() with the callback. In this case for example:

signal_handler_t *handler = obs_output_get_signal_handler(output);
signal_handler_connect(handler, "stop", output_stopped);

Displaying Sources

Sources are displayed on stream/recording via Output Channels with the obs_set_output_source() function. There are 64 channels that you can assign sources to, which will draw on top of each other in ascending index order. Typically, a normal source shouldn’t be directly assigned with this function; you would use a scene or a transition containing scenes.

To draw one or more sources together with a specific transform applied to them, scenes are used. To create a scene, you call obs_scene_create(). Child sources are referenced using scene items, and then specific transforms are applied to those scene items. Scene items are not sources but containers for sources; the same source can be referenced by multiple scene items within the same scene, or can be referenced in multiple scenes. To create a scene item that references a source, you call obs_scene_add(), which returns a new reference to a scene item.

To change the transform of a scene item, you typically would call a function like obs_sceneitem_set_pos() to change its position, obs_sceneitem_set_rot() to change its rotation, or obs_sceneitem_set_scale() to change its scaling. Scene items can also force scaling in to a custom size constraint referred to as a “bounding box”; a bounding box will force the source to be drawn at a specific size and with specific scaling constraint within that size. To use a bounding box, you call the obs_sceneitem_set_bounds_type(), obs_sceneitem_set_bounds(), and obs_sceneitem_set_bounds_alignment(). Though the easiest way to handle everything related to transforms is to use the obs_sceneitem_set_info() and obs_sceneitem_get_info() functions. See Scene Item Functions for all the functions related to scene items.

Usually, a smooth transition between multiple scenes is required. To do this, transitions are used. To create a transition, you use obs_source_create() or obs_source_create_private() like any other source. Then, to activate a transition, you call obs_transition_start(). When the transition is not active and is only displaying one source, it performs a pass-through to the current displaying source. See Transitions for more functions related to using transitions.

The recommended way to set up your structure is to have a transition as the source that is used as the main output source, then your scene as a child of the transition, then your sources as children in the scene. When you need to switch to a new scene, simply call obs_transition_start().

Outputs, Encoders, and Services

Outputs, encoders, and services are all used together, and managed a bit differently than sources. There currently is no global function to save/load them, that must be accomplished manually for now via their settings if needed.

Encoders are used with outputs that expect encoded data (which is almost all typical outputs), such as standard file recording or streaming.

Services are used with outputs to a stream; the RTMP output is the quintessential example of this.

Here’s an example of how an output would be used with encoders and services:

obs_encoder_set_video(my_h264_encoder, obs_get_video());
obs_encoder_set_audio(my_aac_encoder, obs_get_audio());
obs_output_set_video_encoder(my_output, my_h264_encoder);
obs_output_set_audio_encoder(my_output, my_aac_encoder);
obs_output_set_service(my_output, my_service); /* if a stream */

Once the output has started successfully, it automatically starts capturing the video and/or audio from the current video/audio output (i.e. any sources that are assigned to the Output Channels).

If the output fails to start up, it will send the stop signal with an error code in the code parameter, possibly accompanied by a translated error message stored that can be obtained via the obs_output_get_last_error() function.